In a system wherein one or more devices will transfer and receive data using physical busses such as cables, printed circuit board traces, wires, or the like, a transceiver device is often required. Typically, the system devices will both send and receive data on the bus so that the transceiver must provide a bi-directional capability, and the transceiver must drive the data in the direction of the transfer. Known transceiver circuits commonly require two control lines to facilitate this capability, one for enabling the transceiver and the other for determining the direction the bidirectional transceiver will drive data. FIG. I schematically depicts a typical known transceiver with direction (DIR) control lines, the transceiver connecting bidirectional ports A and B.
The transceiver of FIG. 1 continues to provide drive capability in the selected direction so long as the transceiver is enabled, even though the data transfer may be completed and there is no new information being transmitted. This results in unnecessary dynamic power consumption. The designer may limit this power consumption by adding control and timing circuitry, however this requires additional circuitry in the system. Another drawback of known transceivers is that they require two control lines to operate. As systems become more complex, the number of traces and pins needed for coupling the device to busses becomes critical, as these pins and traces are needed for data and status signals. Therefore it is desirable to provide a transceiver circuit which requires no control signals, thus freeing pins and signal traces previously required for control for other uses; and which further consumes driving current and power only when necessary, thereby minimizing system power consumption.